The fabrication of integrated circuits (ICs) involves the formation of features on a substrate that make up circuit components, such as transistors, resistors and capacitors. The devices are interconnected, enabling the IC to perform the desired functions. Interconnections are formed by forming contacts and conductive lines in a dielectric layer using, for example, damascene techniques. A damascene structure, for example, includes a via or contact hole in a lower portion and a trench which is generally wider than the contact hole in an upper portion. The via serves as a contact to a device while the trench contains the conductive line for connecting the device to, for example, other devices.
As critical dimensions (CD) continue to shrink, RC delay contributed by back-end-of line (BEOL) interconnect becomes more and more significant. In the effort to introduce lower k dielectrics for BEOL interconnect, materials such as porous ultra low k (ULK) inter level dielectric (ILD) and lower k SiCxNyHz Cu barrier material have been proposed. With the use of ULK dielectrics, UV curing is required. UV curing is used to form pores to lower the dielectric constant of the film. Additionally, UV curing enhances the mechanical strength of the film.
However, conventional SiCxNyHz films have been found to be unstable when exposed to UV. For example, exposure to UV has been found to cause the dielectric constant of the SiCxNyHz film to increase, the film stress to convert from compressive to tensile, and even cracking of the film which negatively impacts performance and reliability.
From the foregoing discussion, it is desirable to provide a method for forming a Cu barrier with low dielectric constant and high UV resistance.